Translation:Even without seeing you, I would have recognized you by the sound of your voice.
It depends on the verb that follows it, it it is conjugeted with avoir or etre. This is yet another place where you need to remeber wich verbs are conjugated with etre (Remember that "DR & MRS VANDERTRAMP", "ADVENT" or "La maison d'etre" mnemonics)
He would have eaten ==> Il aurait manger
He would have gone ==> il serait aller